Cell phones charged by sound are now closer to becoming a reality

The idea of cell phones being powered by sound is one that has been floating around for years. Back in 2011, Korean researchers were able to demonstrate this technology, but the power output was so low (50 millivolts) that it couldn't have actually charged a cell phone.

Now, a research partnership between Queen Mary's University of London and Microsoft has gotten us excitingly close to this technology becoming a reality. The team has created an energy-harvesting prototype that could be used to charge a phone using everyday background noise. Things like traffic, music, the roar of a stadium and even the very conversations we have while using the phone, could power it.

The technology utilizes zinc oxide nanorods, which when stretched or squashed can produce voltage by converting the mechanical stress into electricity. Those nanorods are applied to a surface and when that surface is subjected to stretching or squashing, the nanorods can generate a high voltage.

QMUL says, "The nanorods respond to vibration and movement created by everyday sound, such as our voices. Electrical contacts on both sides of the rods are then used to harvest the voltage to charge a phone."

The researchers came up with a way to make production of the technology easier to scale and cheaper by spraying the nanorods onto a plastic sheet. When heated to 90 degrees Celsius, the nanorods then grew all over the sheet. The team then came up with a method for using aluminum instead of gold as an electrical contact, which also reduces costs.

The prototype device is the same size as a Nokia Lumia 925 and generates five volts -- enough to charge a phone and far more than the 50 millivolts achieved a few years ago.

Dr Joe Briscoe from QMUL’s School of Engineering and Materials Science said, "Being able to keep mobile devices working for longer, or do away with batteries completely by tapping into the stray energy that is all around us is an exciting concept. This collaboration was an excellent opportunity to develop alternative device designs using cheap and scalable methods. We hope that we have brought this technology closer to viability."